The present invention relates to a light-beam scanning apparatus which generates multi-directional light-beams in a predetermined space, more particularly to a light-beam scanning apparatus used in a device for reading a bar-code attached on an article.
More and more supermarkets have been introducing point-of-sale (POS) systems to speed up check-out of sales and to improve inventory control.
A POS system makes use of a bar-code reader which reads bar-codes attached on articles and converts the read codes to data for computer processing; a computer which processes the data to identify the article, add the price code on the sales total, and enter the sale for inventory control; and a cash register connected between the bar-code reader and the computer which outputs the sales total for the cashier.
The bar-code reader includes a light-beam scanning apparatus. The light-beam scanning apparatus includes a light-beam emitting device, such as a laser tube, for providing a laser beam to a hologram disk rotating at a predetermined speed, a deflection system for deflecting the laser beam emitted from the laser tube to the hologram disk, a mirror system deflecting the laser beams diffracted by the hologram disk to form a desired scanning light pattern in a predetermined space, and a reading window placed in the path of the beams reflected from the final mirrors of the mirror system. The light-beam scanning apparatus further includes a light detector sensing the scattered light from the bar-code and converting the sensed signal to an electrical signal, and a decoding circuit.
A usual bar-code reader can read not only standard bar-code symbols of the Universal Product Code (UPC), European Article Number Code (EAN), Japanese Article Number (JAN), etc., but also the truncated symbols now in common use, wherein the length of the bars is reduced. To accomplish this, the light-beam scanning apparatus must provide a desired scanning line pattern consisting of a plurality of light beam traversing in multi-directions a predetermined zone of travel of an article.
U.S. patent applications having Ser. Nos. 162,867 and 162,868 both now abandoned (laid-open in corresponding Japanese Unexamined Patent Publication (Kokai) No. 57-44119) disclose light-beam scanning apparatuses which form light beam patterns consisting of multi-directional scanning lines for traversing the bar-code. In these apparatuses, the laser beam is emitted to the hologram disk from a position below the disk. The diffracted laser beams are directed to and deflected by a set of deflecting mirrors placed above the hologram disk to obtain a predetermined light path length. The beams are finally emitted to a scanning region of an article through a reading window. This optical system, however, results in a considerably large height from the bottom of the apparatus to the reading window. This is disadvantageous for recent POS systems, where the cashiers are seated behind the scanners rather than standing alongside them.
U.S. patent application having Ser. No. 271,344 now U.S. Pat. No. 4,415,224 (laid-open in corresponding Japanese Unexamined Patent Publication (Kokai) No. 57-204022) discloses a similar apparatus with an improved hologram disk to ensure correct bar-code reading. This apparatus, however, has the same optical configuration.